lesson 5 or 6 notes

Stack-- first in last out, pop, push, etc

Queue-- first in first out


def balanced(str:String): Boolean = {
	brackets = HashMap('(' -> ')', '[' -> ']', '{' -> '}')
	stk = Stack.empty[Char]
	for(c <- str) {
		if(brackets.contains(c)) stk.push(brackets(c))
		else if(stk.isEmpty || stk.pop != c) return false
	}
	stk.isEmpty
}

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Recursion review

def sum(list:List[Int]): Int = {
	if(list.isEmpty) 0
	else list.head + sum(list.tail)
}

list(1,2,3,4)
1  DIVIDE  (2,3,4)
   CONQUER  (9)
   GLUE
list.head + sum(list.tail)
10


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HashMap stuff

import scala.collection.immutable.HashMap

val pets = HashMap("cat" -> 1, "dog" -> 2, "tank" -> 100)
this is immutable because of val i guess

val newPets = pets + ("infantry" -> 1)

===

Set-- stuff in a set is unique

mySet = TreeSet(2,4,6,8)
mySet(10) => false


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LinkedList

case class SList(item:Int, next:SList)
this is just the exact same as the normal List class except it uses item and next instead of head and tail

def length(list: SList): Int = {
	if(list == null) 0
	else 1 + length(list.next)
}